1 NEAR-FIELD DIRECT ANTENNA MODULATION PRESENTED BY NABEEL SALAM NO.44 S7 EC GUIDED BY Mr AJAYAN K.K Lecturer ECE Dept

2 OUTLINE Conventional Transmitter Architecture Modulation at Baseband Direct Antenna Modulation Implementation of NFDAM Applications of NFDAM Improvements 60 Ghz Transmitter and NFDAM chip Conclusions

3 CONVENTIONAL TRANSMITTER ARCHITECTURE Signal is modulated at base-band Antenna transmits the same information to all directions Signals that are transmitted in different directions differ only in their power level and time delay

4 MODULATION AT BASEBAND In conventional architectures, the radiation pattern of the antenna remains unchanged at each symbol transmission For a fixed antenna pattern, any change in the phase or amplitude of the base-band signal is detectable in the desired direction as well as the undesired direction

5 DIRECT ANTENNA MODULATION In the above transmitter architecture, the far-field of the antenna changes at each symbol transmission, but the change in the far-field is not the same for all angles The antenna pattern needs to be varied at the speed of symbol-rate to be able to modulate the signal

6 DAM GENERAL CONCEPT Diode switch ON (V > Vd) Short circuit effectively exists between patch antenna and ground plane Antenna radiation effectively ceases Diode Switch OFF (V < Vd) Diode at high impedance Antenna fully radiates at resonance

7 ANTENNA MODULATION VIA REFLECTOR SWITCHING Switching affects the scattering characteristics of the reflector The phase and amplitude of the reflected signal vary by switching

8 ARBITRARY SIGNAL MODULATION It is possible to increase the number of the constellation points by adding more reflectors and switches Each additional switch doubles the number of the constellation points

9 NEAR FIELD DIRECT ANTENNA MODULATION Reflectors are placed in the near-field of the antenna CMOS switches can be used to implement the NFDAM transmitter

10 NEAR FIELD DIRECT ANTENNA MODULATION An efficient switching PA can be used while transmitting a non-constant envelope modulated signal As the PA amplifies the non-modulated carrier signal, it can be narrow-band

11 SECURE COMMUNICATION LINK The angle-dependent modulation provides a secure communication link The correctly modulated signal is only transmitted to the desired direction

12 ERROR RATE DUE TO SIGNAL SCRAMBLING By changing the angle, some of the constellation points move to adjacent cells and introduce error

13 NOISE INDEPENDENT ERROR RATE A total number of 210 equally-spaced points are selected Bore-sight is set to be the desired direction in this example The desired direction can be steered by choosing a different set of switching combinations

14 ENHANCED SECURITY USING REDUNDANCY For a total number of N switches on the reflectors, 2 N configurations exist. For example: N=90→2 90 ~10 27 Redundancy can be used to generate a single constellation point in the desired direction with many different switching combinations

15 MULTIPLE BEAM TRANSMISSION Transmission of two independent streams in two directions at full rate without resorting to multiple access techniques

16 SPECTRAL CONTROL To control the out-of-band EM emission radiated by the antenna Directly moving from A to B causes out of band emissions Redundancy concept is used to render any trajectory using multiple intermediate points

17 PHASED ARRAY CONFIGURATION Each NFDAM system can behave as a single element in a phased array configuration NFDAM system can control the information beamwidth Phased-array functionality can be used to narrow the power beamwidth

18 60 Ghz NFDAM TRANSMITTER Coverage of the signal constellation diagram is a function of size, shape, and location of the reflectors as well as their distance from the main antenna

19 TRANSMITTER WITH OPTIONAL COARSE CONROL UNIT Coarse control unit acts as quadrant selector Control signals A and B can take values 1 and -1

20 SWITCH AND REFLECTOR Switches with a relatively high ratio of OFF to ON impedances must be implemented A circular shielded transmission line is used to connect the drain and source of the NMOS switch OFF impedance of 70 ohm at 60Ghz can be obtained

21 NFDAM CHIP MICROGRAPH The chip includes on-chip antennas, switches, and reflectors as well as a digital control unit, receiver, and LO generation circuitry

22 CONCLUSIONS Concept of Near-Field Direct Antenna Modulation has been introduced NFDAM can be effectively used to establish a secure communication link Multiple beam transmission is possible using NFDAM without any multiple access techniques Spectral Control can be effectively done using NFDAM NFDAM transmitter can be used in a phased array configuration to improves power efficiency An example of a 60 Ghz NFDAM transmitter has been discussed

23 REFERENCES A. Babakhani, D.B. Rutledge, and A. Hajimiri, ”Near-field Direct Antenna Modulation,” IEEE Microwave Magazine, vol. 17, no. 6, Feb. 2009, pp A. Babakhani, D.B. Rutledge, and A. Hajimiri, “Transmitter architectures based on near-field direct antenna modulation,” IEEE J. Solid-State Circuits, vol. 43, no. 12, Dec. 2008, pp – 2682 A. Babakhani, D.B. Rutledge, and A. Hajimiri, “A near- field modulation technique using antenna reflector switching,” in IEEE ISSCC Dig. Tech. Papers,vol.10, no. 5, Feb. 2008, pp. 188–189

24 THANK YOU

25 QUESTIONS?